There is known a spark plug in which a tip is connected to an electrode base metal through a fusion zone (see, for example, Japanese Patent Application Laid-Open (kokai) No. 2017-228430).
A spark plug of this type is required to employ a technique for restraining separation at the interface between an electrode base metal and a fusion zone so as to prevent detachment of a tip from the electrode base metal even in the event of development of cracking from an end of the interface between the electrode base metal and the fusion zone.
The present invention has been conceived to meet the above requirement. An advantage of the invention is a spark plug capable of restraining separation at the interface between an electrode base metal and a fusion zone.